From WO 2004/083633 A1 a sectioned wind turbine tower is known. In order to transport large size windmill towers the steel tower for a windmill comprises a number of cylindrical or tapered tower sections which are partly subdivided into two or more elongated shell segments. The shell segments combine into a complete tower section by means of vertical flanges which are connected by bolts. Sectioning is mainly done in order to achieve manageable tower units, both in relation to transportation and to lifting.
In EP 2 006 471 A1 it has been proposed to further split each section into tower segments. Each tower section is divided into segments which will be assembled by means of splice plate connections during installation. One advantage of this vertical segmentation is that the segments can be staged during a storage and transportation and therefore do not require as much space as for the tubular sectioned ones. Typically the tower segments have a polygonal cross-section.
In WO 2009/097858 A1 a tower element for a tower for a wind power plant is disclosed, where several tower elements with an outer surface and an inner surface are mounted on top of each other. The periphery of the tower element is made up of a number of segments provided with inwardly facing flanges at the longitudinal sides, the flanges being connected to corresponding flanges on laterally arranged segments. The individual segments are made with an overlap on the outer surface in the transverse joints and with a butt joint at the inwardly facing flanges.
In recent years the size of wind turbine towers has increased substantially which requires an assembly rig so that wind turbine towers can be assembled on an installation side quickly and safely.